does the energy (enthalpy) decreases as the vc-relaxation progresses ?
The local structure around the defect may be quite different. It may
just take long.
I would start by performing a fixed cell relaxation with the cell
parameters fixed at the undefected equilibrium values. And only after
that I would start the vc-relax calculation from the so relaxed
configuration to evaluate the vacancy formation volume. The local
arrangement around the defect should be already more or less ok (if the
supercell is large enough).
HTH
stefano
On 06/08/2017 16:40, Manu Hegde wrote:
Hello,
I am trying to optimize anatase TiO2 supercell with 48 atoms. The
supercell converges in 15 BFGS cycles for a perfect cell. But when I
introduce defect (by removing one of the oxygen atom), the vc-relax is
not t all converging. I am using the same parameters in both the
cases. Can anyone give some feedback on this.?. Here is my input,
&control
calculation = 'vc-relax' ,
restart_mode = 'from_scratch' ,
outdir = '/work/mhegde/tmp_tiodef/',
pseudo_dir = '/home/mhegde/tio_project/def_tio/',
prefix = 'tioan',
verbosity = 'high',
/
&system
ibrav = 0,
nat = 47,
ntyp = 2,
ecutwfc =40,
ecutrho=400,
occupations='smearing',
degauss=0.003
/
&electrons
conv_thr = 1.D-6,
mixing_beta=0.1
/
&ions
ion_dynamics='bfgs'
/
&cell
cell_dynamics='bfgs'
/
ATOMIC_SPECIES
Ti 47.867000 Ti.pw91-nsp-van.UPF
O 15.99900 O.pw91-van_ak.UPF
ATOMIC_POSITIONS angstrom
Ti 0.00000000 2.84182500 1.20970000
Ti 1.89455000 2.84182500 3.62910000
O 0.00000000 0.94727500 1.99939216
O 0.00000000 2.84182500 4.41879216
O 1.89455000 0.94727500 2.83940784
Ti -1.89455000 0.94727500 -3.62910000
Ti 0.00000000 0.94727500 -1.20970000
O -1.89455000 -0.94727500 -2.83940784
O -1.89455000 0.94727500 -0.42000784
O 0.00000000 -0.94727500 -1.99939216
O 0.00000000 0.94727500 -4.41879216
Ti 0.00000000 -0.94727500 1.20970000
Ti 1.89455000 -0.94727500 3.62910000
O 0.00000000 -2.84182500 1.99939216
O 0.00000000 -0.94727500 4.41879216
O 1.89455000 -2.84182500 2.83940784
O 1.89455000 -0.94727500 0.42000784
Ti -1.89455000 -2.84182500 -3.62910000
Ti 0.00000000 -2.84182500 -1.20970000
O -1.89455000 2.84182500 -2.83940784
O -1.89455000 -2.84182500 -0.42000784
O 0.00000000 2.84182500 -1.99939216
O 0.00000000 -2.84182500 -4.41879216
Ti -3.78910000 2.84182500 1.20970000
Ti -1.89455000 2.84182500 3.62910000
O -3.78910000 0.94727500 1.99939216
O -3.78910000 2.84182500 4.41879216
O -1.89455000 0.94727500 2.83940784
O -1.89455000 2.84182500 0.42000784
Ti 1.89455000 0.94727500 -3.62910000
Ti -3.78910000 0.94727500 -1.20970000
O 1.89455000 -0.94727500 -2.83940784
O 1.89455000 0.94727500 -0.42000784
O -3.78910000 -0.94727500 -1.99939216
O -3.78910000 0.94727500 -4.41879216
Ti -3.78910000 -0.94727500 1.20970000
Ti -1.89455000 -0.94727500 3.62910000
O -3.78910000 -2.84182500 1.99939216
O -3.78910000 -0.94727500 4.41879216
O -1.89455000 -2.84182500 2.83940784
O -1.89455000 -0.94727500 0.42000784
Ti 1.89455000 -2.84182500 -3.62910000
Ti -3.78910000 -2.84182500 -1.20970000
O 1.89455000 2.84182500 -2.83940784
O 1.89455000 -2.84182500 -0.42000784
O -3.78910000 2.84182500 -1.99939216
O -3.78910000 -2.84182500 -4.41879216
K_POINTS {automatic}
2 2 2 0 0 0
CELL_PARAMETERS angstrom
7.57820000 0.00000000 0.00000000
0.00000000 7.57820000 0.00000000
0.00000000 0.00000000 9.67760000
Thanks,
Manu
(University of Waterloo)
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